1. Field of the Invention
The present invention relates to a pickup device which, for example, writes or reads data into or from an optical recording medium.
2. Description of Related Art
There has been a known pickup device which writes or reads data into or from an optical recording medium, e.g., optical disks such as a DVD (Digital Versatile Disk), a CD (Compact Disk), and the like.
The pickup device is constituted by including a laser light source as a light source which irradiates a light beam onto an optical disk, a grating as an optical element provided in the middle of an optical path extending toward the optical disk from the laser light source, and a pickup base on which the laser light source and the grating are mounted.
The pickup base is provided with a communication hole. The communication hole has, at an end, a light source attachment for attaching the laser light source, and an optical element attachment for attaching an optical element such as a grating or the like is provided at another end of the pickup base. The laser light source is attached to the light source attachment, and the grating is attached to the optical element attachment. The laser light source and the grating are provided to be coaxial with each other.
Provided on the pickup base are a beam splitter which reflects laser light emitted from the laser light source toward the optical disk, a lens which converges laser light, and an optical element such as a light detector which detects reflection light from the optical disk.
The grating, for example, serves to diffract the laser beam from the laser light source and split the light beam into one main beam and two sub-beams. The sub-beams split by the grating are irradiated at a predetermined angle onto data tracks of the optical disk. The reflection light thereof is detected by the optical detector of the pickup device. Based on a detection signal from the optical detector, tracking adjustment or the like is performed on the main beam.
The laser light source generates heat when it irradiates laser light. When the laser light source and the grating are thus respectively provided at one end and another end of the communication hole, however, the heat generated from the laser light source easily accumulates in the communication hole, so that the temperature of the laser light source increases. As the temperature of the laser light source increases, a problem arises in that the characteristics of the laser light source deteriorate or the lifetime thereof is shortened.
It is considered that, to radiate the heat of the laser light source, the pickup base may be formed of metal material having a good heat transmission characteristic, and a heat-radiating plate may be provided for the laser light source. In recent years, however, the pickup base has been made of synthetic resin owing to demands for cost reduction. In addition, laser light sources, which are compatible with both of the DVD and CD or write data onto optical disks, have come to be used. The amount of heat generated from these laser light sources is so large that the heat-radiating plate is not enough to achieve sufficient heat radiation for these laser light sources.